Hepatitis C virus (HCV), a positive-strand RNA flavivirus, is a leading cause of liver disease worldwide. Although acute infection can be asymptomatic, approximately 80% of patients fail to clear the virus resulting in a chronic infection associated with significant liver disease, including steatosis, insulin-resistance, fibrosis, cirrhosis and hepatocellular carcinoma (Alter & Seeff (2000) Semin. Liver Dis. 20:17-35). As such, HCV-related cancer accounts for over 50% of hepatocellular carcinoma cases and over 30% of liver transplants performed in the United States. Despite this obvious public health burden, there is no vaccine to prevent infection.
HCV is thought to enter cells via receptor-mediated endocytosis beginning with binding of the viral particle to a series of cell surface receptors, including the tetraspanin CD81 (Pileri, et al. (1998) Science 282:938-41), the scavenger receptor class B member I (SR-BI) (Scarselli, et al. (2002) EMBO J. 21:5017-25) and the tight-junction proteins claudin-1 (Evans, et al. (2007) Nature 446:801-5) and occludin (Liu, et al. (2009) J. Virol. 83:2011-4; Ploss, et al. (2009) Nature 457:882-6), followed by clathrin-mediated endocytosis (Blanchard, et al. (2006) J. Virol. 80:6964-72; Meertens, et al. (2006) J. Virol. 80:11571-8) and class II fusion (Garry & Dash (2003) Virology 307:255-65) between the virion envelope and the endosomal membrane. Additionally, the low-density lipoprotein receptor (LDLR) (Agnello, et al. (1999) Proc. Natl. Acad. Sci. USA 96:12766-12771; Monazahian, et al. (1999) J. Med. Virol. 57:223-229; Wunschmann, et al. (2000) J. Virol. 74:10055-10062), asialoglycoprotein receptor (Saunier, et al. (2003) J. Virol. 77:546-559), protocadherin β5 (Womg-Staal, et al. (2008) 15th International Symposium on Hepatitis C Virus & Related Viruses. San Antonio, Tex.), and glycosaminoglycans (heparan sulfate) (Barth, et al. (2003) J. Biol. Chem. 278:41003-41012; Barth, et al. (2006) J. Virol. 80:10579-10590; Bartosch, et al. (2003) J. Exp. Med. 197:633-642) have been implicated; however, the role of those agents has not been conclusively proven to be essential for HCV entry. In addition, it has been shown that the HCV particle is not only uniquely enriched in cholesterol (Aizaki, et al. (2008) J. Virol. 82:5715-24), but that depletion of cholesterol ablates particle infectivity (Aizaki, et al. (2008) supra; Kapadia, et al. (2007) J. Virol. 81:374-83).
While clinically approved HCV entry inhibitors have not been identified, a number of agents have been described for inhibiting HCV replication. For example, the current treatment option for HCV is a combination therapy with interferon (IFN) and ribavirin. However, this combination has toxic side effects, marginal efficacy, and limited availability (Firpi & Nelson (2007) Arch. Med. Res. 38:678-690; Foster & Mathurin (2008) Antivir. Ther. 13:3-8). In addition, US 2008/0161324 describes a series of HCV replication inhibitors identified using a replication assay. However, the compounds identified therein were not shown to prevent infection and spread of HCV. As such, the identification of novel and more potent antivirals targeting other aspects of the viral life cycles (e.g., entry inhibitors) is imperative.
Ezetimibe, a 2-azetidinone class of drug, is an anti-hyperlipidemic, cholesterol-lowering medication, currently approved for use in humans by the U.S. Food and Drug Administration (FDA); the drug has been shown to potently inhibit cholesterol absorption in vivo, thus lowering plasma total and LDL cholesterol in treated individuals (Bays, et al. (2008) Expert Rev. Cardiovasc. Ther. 6:447-470). Data indicate that the protein known as Niemann-Pick C1-like 1 (NPC1L1) is the molecular target of ezetimibe in cells (Garcia-Calvo, et al. (2005) Proc. Natl. Acad. Sci. USA 102:8132-8137). Additional studies indicate that SR-B1 might be the target of ezetimibe action in cells (Labonte, et al. (2007) Biochim. Biophys. Acta 1771:1132-1139). Ezetimibe is marketed under the trade names EZETROL and ZETIA. It is also marketed in combination with the statin drug simvastatin (ZOCOR) under the trade names VYTORIN and INEGY. It is indicated as an adjunct to dietary measures in the management of hypercholesterolaemia, homozygous sitosterolemia (phytosterolemia), and the treatment of mixed hyperlipidaemia when used in combination with fenofibrate.